/*
 * @Description: In User Settings Edit
 * @Author: your name
 * @Date: 2019-08-29 16:20:54
 * @LastEditTime: 2019-08-29 16:54:23
 * @LastEditors: Please set LastEditors
 */
/*
 * @lc app=leetcode.cn id=21 lang=javascript
 *
 * [21] 合并两个有序链表
 *
 * https://leetcode-cn.com/problems/merge-two-sorted-lists/description/
 *
 * algorithms
 * Easy (56.67%)
 * Likes:    591
 * Dislikes: 0
 * Total Accepted:    102K
 * Total Submissions: 179.6K
 * Testcase Example:  '[1,2,4]\n[1,3,4]'
 *
 * 将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 
 * 
 * 示例：
 * 
 * 输入：1->2->4, 1->3->4
 * 输出：1->1->2->3->4->4
 * 
 * 
 */
/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
// var mergeTwoLists = function(l1, l2) {
//     if(l2 == null) return l1
//     if(l1 == null) return l2
//     if(l1.val < l2.val){
//         l1.next = mergeTwoLists(l1.next , l2)
//         return l1
//     }else{
//         l2.next = mergeTwoLists(l2.next , l1)
//         return l2
//     }
// };

var mergeTwoLists = function(l1,l2){
    const result = new ListNode()
    let next = result
    while(l1 && l2){
        if(l1.val > l2.val){
            next.next = l2
            l2 = l2.next
        }else{
            next.next = l1
            l1 = l1.next
        }
        next = next.next
    }
    next.next = l1 || l2
    return result.next
}


